Matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) has been applied to achieve a qualitative and quantitative evaluation of glycated globins on a wide number of healthy and diabetic subjects. The method allowed us to establish that both alpha- and beta-globins are glycated and that, in addition to simply glycated products, other species are detected. Investigations by different sample treatments and by analysis of the glycated beta-globin fraction obtained by preparative chromatography indicated that these species correspond to glyco-oxidized globins. Consequently MALDI-MS can be validly employed to evaluate not only the glycation level, but also the degree of oxidative stress. The percentages of glycated and glycooxidized species were calculated from the related MALDI spectra by the measurement of the related peak areas, without any other treatment of data. A linear relationship between HbA1c values and the total percentage of glycated and glyco-oxidized globins has been found, and its slope (< 1) has been rationalized by the uncorrected evaluation of glycated globins content in the standard samples employed for HbA1c measurements.

A new method, based on matrix-assisted laser desorption/ionization (MALDI) measurements, has been developed for the evaluation of the glycation level of globins, a relevant parameter for diabetes control. It shows high levels of reproducibility and specificity, allowing the different glycated and glyco-oxidized products of both alpha- and beta-globins to be distinguished. Such specificity is reflected in its possible diagnostic use not only for the control of diabetes, but also for the occurrence of 'oxidative stress'. The comparison, for the same samples, of the obtained MALDI data with the related HbA1c values, determined by a high performance liquid chromatographic method, allowed it to be established that HbA1c percentages are not, as usually retained, related to the simply glycated beta-globin, but to the whole pool of glycated and glyco-oxidized alpha- and beta-globins.

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Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has been employed for the evaluation of the glycation level of IgG from healthy subjects and also from well- and badly-controlled diabetic patients. The measurements have been performed on untreated plasma protein fractions. The data obtained have shown that a clear mass increase, originating from non-enzymatic glycation processes, is observed in the case of diabetic patients: for well-controlled ones it is in the range 512-1565 Da, while it becomes 827-4270 Da for badly-controlled diabetic patients. This approach indicates that MALDI mass spectrometry is a highly specific tool that can be employed in the metabolic control of diabetic patients and in studies relating the IgG glycation level to possible immunological impairment.

The electron ionization mass spectrometric behaviour of melatonin (N‐acetyl‐5‐methoxytryptamine) and of a series of its isomers has been studied with the aid of metastable ion experiments. The data show that the different positions of the substituents on the indole ring influence the fragmentation patterns and the relative abundances of the generated ions. © 1998 John Wiley & Sons, Ltd.